Many different types of cutting tools are available for use in a variety of applications. In most industrial situations, either the cutter is rotated or otherwise moved, and the workpiece is maintained stationary. In other situations, the cutter is stationary and the workpiece is rotated or otherwise moved. In yet other applications, both the cutter and the workpiece may be moved at the same time.
Reinstatement cutting machines are special applications where a cutter is utilized for cutting an opening in a plastic liner installed in a deteriorated underground pipe, e.g., a main. The reinstatement cutting machine is moved through the lined main until it is at a location where a lateral pipe connects to the main pipe. The plastic liner previously installed in the main covers the opening to each lateral pipe. The function of the reinstatement cutting machine is to cut a circular opening in the plastic liner where the lateral pipe opens into the main pipe. This operation reinstates the ability of fluids to flow from the lateral pipe into the lined main pipe.
Cutters mounted to reinstatement cutting machines generally rely on three degrees of motion, including a radial motion with regard to the axis of the main pipe, rotational movements in a plane orthogonal to the axis of the main pipe, and axial movements along the axis of the main pipe. Often, the longitudinal movements of the reinstatement cutting machine itself provide one direction of movement of the cutter. The bit of the cutting machine can be mounted to a platform that provides radial movement of the bit toward the sidewall of the liner, as well as rotational movements during the cutting operation. In other types of cutting machines, the platform can be constructed to provide all three types of movements of the bit to accomplish the cutting of a hole in the liner to provide an opening to the lateral. Because the reinstatement cutting machine is moved along the liner of the main, it cannot be directly controlled or observed. Accordingly, remote controls are used to remotely control the various movements of the cutting machine. Video cameras are typically used ahead of the cutting machine to allow the cutting operation to be viewed remotely by the operator of the remote controls.
As can be appreciated, when the reinstatement cutting machine is moved into an underground pipe, the entire mechanism, including the cutter itself, must be very reliable. Otherwise, the entire apparatus must be removed from the pipe, which is not often easy, as a cutter may fail or the mobility of the cutting machine may be lost, while the bit is extended radially into the sidewall opening of the main pipe. The bit mechanism is sometimes destroyed during the forceful removal of the reinstatement cutting machine from the main pipe. In other situations, the reinstatement cutting machine and any associated camera equipment must be removed from the main pipe if the bit of the cutter fails. The bit can fail if it becomes dull, broken or becomes loose from its mounting chuck. As can be appreciated, the more complicated a cutter becomes, the more likely a failure will occur. In addition, the more complicated the design and construction of a cutter, the more costly the device becomes.
The various assemblies of a reinstatement cutting machine are generally driven by electrical motors. The motors are housed in a case with the other apparatus and sealed so that moisture and liquids cannot enter in to the internal working of the machine. However, in the event a seal becomes defective, the life of a motor can be seriously shortened. While the gear assemblies may be damaged by moisture, such damage may be repairable, whereas, moisture that has leaked into a motor may damage the same beyond repair. The result is that the machine is required to be removed from the underground pipe and disassembled to replace the defective motor. One solution may be to employ water-proof motors. However, this solution is extremely expensive.
Air pressure is utilized in many reinstatement cutting machines to drive the cutting bit. In some machines, the air pressure is coupled directly to the air-driven motor. This is the case in reinstatement cutting machines of the type that move in a pipe main with the cutter mounted to the back of the reinstatement machine. Here, the air pressure hose is towed by the reinstatement cutting machine and coupled directly to the air-driven motor. In other situations, the reinstatement cutting machine moves in the pipe main with the cutter mounted to the front of the machine. In this case, the air pressure hose is towed by the machine, but the air pressure must be routed either around the machine, or through the machine to the front-mounted air-driven cutter motor. When routing the air pressure around the reinstatement cutting machine, a separate metal pipe is generally attached to the outer surface of the reinstatement cutting machine to carry the air pressure from the back of the machine to the front-mounted cutter motor. This is acceptable, but the external air pressure tube increases the effective diameter of the machine, thereby limiting the diameter of the main pipe that can be reinstated.
In other types of reinstatement cutting machines, air pressure is coupled through the machine itself from the back thereof to the front-mounted cutter motor. This solves the problem attendant with external-mounted air pressure tubes, but creates other problems. One problem created with the use of internal air passages is that of condensation that forms internal to the cutting machine and exposure of the same to the motors, bearings and gear apparatus. This is believed to be the result of the Bernoulli principle, in which the change of velocity of the pressurized air creates temperature changes in the material that conducts the air pressure. In other words, when the velocity of the air carried by the internal passage changes due to the starting and stopping of the air-driven motor, the metal parts of the machine affected by the temperature change may allow moisture to condense thereon. Metal parts that have an elevated operating temperatures, such as motors, may accelerate the condensation of the moisture in the air that is captured in the cutting machine. The collection of moisture on the various components of the cutting machine, especially motors, substantially reduces the life and reliability of the cutting machine.
From the foregoing, it can be seen that a need exists for a motor module which houses all of the electrical motors utilized to drive the components of the cutting machine. Another need exists for a motor module that is separate and sealed from the other apparatus of the cutting machine. Yet another need exists for a technique that enables air pressure to be coupled internal to the cutting machine without the attendant problems of condensed moisture.